The present invention relates generally to leak testing apparatuses and methods and, more particularly, to a leak testing apparatus and method related to manufacture of compressed natural gas automobiles.
One of the problems associated with manufacture of compressed natural gas or CNG automobiles has been in the testing of the fuel system for leaks during the assembly process without unnecessary delay of the assembly line. The problems created by testing for fuel system leaks is that such testing, in the past, has been a relatively time-consuming process that was not capable of being accomplished in the time allotted on an automated assembly line. Accordingly, attempts in the past to provide a CNG mass-produced automobile have not been favorably received.
With reference to FIG. 1, a prior art leak testing apparatus and method is schematically illustrated. As shown in FIG. 1, a filling conduit 12 extends from a filling receptacle 14 to the input port of a CNG tank 16. A manual input valve is provided at the CNG input port and a manual output valve is provided at an output port of the CNG tank 16. A supply conduit 18 extends from the CNG tank output valve to a fuel pressure regulator assembly 20. From the fuel pressure regulator assembly 20 a fuel feed line (not shown) extends to a fuel rail (not shown) which communicates with a series of CNG injectors. Each of the joints or connections in the fuel system must be checked for leaks prior to the automobile leaving the factory and preferably, during the assembly process. However, in the past the fuel system leak checking was done in a single step and required about 15 minutes to accomplish a full check of the fuel system. Moreover, the prior art leak checking method required pressurization of the CNG tank 16, which is wasteful of pressurizing fluid and time consuming.
The prior art method for testing leaks in the fuel system requires pressurization of the entire system by injecting pressurizing fluid via the filling receptacle 14 and filling conduit 12. Once the system, at least to the pressure regulator assembly 20, was pressurized, the tank output valve could be closed and sensors could be used to sense leakage of pressurizing fluid. Thereafter, the pressure regulator assembly 20 could be activated to introduce pressurized gas into the fuel feed line and the fuel rail, and further sensing for leakage of pressurizing fluid would occur. As stated previously, pressurizing and sensing of the fuel system typically required 15 minutes, whereas, in modern assembly lines, each step the process is given a certain time period, for example 60 seconds. Accordingly, the known leak sensing method and apparatus is incompatible and not useful on modern assembly lines.
Accordingly, there exists a need in the art for a method and apparatus for testing leaks in CNG fuel systems for automobiles which can be performed quickly and reliably. Moreover, there exists a need in the art for a CNG leak testing method and apparatus that can be incorporated into an automobile assembly line.